Method for heat sealing



A r l 22, 1969 R B R ET A; 3,439,590

METHOD FOR HEAT SEALING Sheet Filed Dec. 15, 1964 INVENTORS' WILLIAMROSENBERG CHARLES J. F DOUGLAS JOHNSON GRAFTON ROSS W. HOHMAN FIG. 2.

ATTORNEY April 22, 1969 w. ROSENBERG ET AL METHOD FOR HEAT SEALING SheetFiled Dec. 15, 1964 FIG. 4.

PAPER STOCK} FIG FIG. I6.

INVENTORJ WILLIAM ROSENBERG CHARLES J. GRAFTON F. DOUGLAS JOHNSON ROSSW. HOHMAN ATTORNEY April 22, 1969 W. ROSENBERG ET AL METHOD FOR HEATSEALING Sheet Filed Dec. 15, 1964 INVENTORS WILLIAM ROSENBERG ATTORNEYCHARLES J. GRAFTON F. DOUGLAS JOHNSON ROSS. W. HOHMAN GEM:

Sheet 4 of 4 w. ROSENBERG ET AL METHOD FOR HEAT SEALING INVENTORS April22, 1969 Filed Dec I 500 2. Me E T ROSS w. HOHMAN wig/{WW ATTORNEYUnited States Patent M 3,439,590 METHOD FOR HEAT SEALING WilliamRosenberg, Charles J. Crafton, Frederick Douglas Johnson, and Ross W.Hohman, Baltimore, Md., as-

signors to Maryland Cup Corporation, Owings Mills, Md., a corporation ofMaryland Filed Dec. 15, 1964, Ser. No. 418,434 Int. Cl. C09j /10; B32b31/20; B31b 17/60 US. Cl. 9355.1 2 Claims This invention relates topaper cups; and it is more particularly concerned with the manufactureof such cups.

A popular form of paper cup in wide, general use is known in theindustry as the fiat bottom cup. It is made, generally, of a circularbottom wall having a downwardly extending flange and a frustoconicalside wall the bottom of which fits around the flange of the bottom wall.A marginal extension of the side wall is bent around the flange of thebottom wall and securely fitted to it by a bottom expander. These twoparts, so arranged relative to each other, are glued together, the gluebeing applied at a convenient step in the assembly of the blanks whichform these parts.

In recent years, the industry has developed many improvements in thesecups. A significant improvement is the coating of the inside surfaces ofthe cups with a plastic material to form a barrier against hot liquids,like coffee, and cold liquids to prevent them from coming into contactwith and being absorbed by the porous paper. In many instances, thesecoatings are applied to the cup after their manufacture.

It has been suggested that the plastic coating might be applied to thesurface of the blank members before they are assembled and that thepaper coating be utilized as the sealing agent in lieu of theconventional glue.

Attempts to carry out this procedure have met with many difiiculties. Animportant difficulty resides in the fact that the plastic material mustbe heated to the point of tackiness in order for it to be available as abonding agent. However, in this tacky condition, it is diificult tohandle the blanks on the assembly machinery. Slippage necessary toposition the blank sections relative to each other is markedly reduced.Also, the surface of the mandrels are exposed to the tacky plasticcausing the machinery to become fouled and requiring frequent stoppageand cleaning of the parts affected.

Also, it has been a problem to produce cups of this kind from laminatedsheets, such as paper cup stock laminated with aluminum foil, aformidable difficulty being the partial delamination or separation ofthe plies from each other under the heat required to soften the plasticcoating. As a result, partial separation of the plies is encountered.

The general object of the present invention is the provision of animproved method of manufacturing flat bottom cups from plastic-coatedblanks.

A specific object of the invention is the provision of such an improvedmethod which is adaptable to commercial automatic cup-making machineryand by means of which the plastic coating does not interfere oradversely affect the operation of the machinery.

Another object of the invention is the provision of such a method whichis highly effective and reliable in commercial operations.

A further object of the invention is the provision of 3,439,590-Patented Apr. 22, 1969 such a method which is applicable to theproduction of cups from laminated sheet material, such as sheets ofordinary paper cup stock laminated with aluminum foil.

These and still further objects, advantages, and features will appearmore fully from the following description together with the accompanyingdrawings.

In the drawings:

FIGURE 1 is a schematic plan view of a rotatable turret forming part ofa typical cup-making machine including the radial mandrels withmodifications in accord ance with this invention and illustrating theseries of steps in the formation of the cups.

FIGURE 2 is a perspective view of a blank member used in forming theside wall of the cup.

FIGURE 3 is a perspective view of a blank member used in forming thebottom wall of the cup.

FIGURE 4 is a cross-sectional view along the line 4-4 of FIGURE 2.

FIGURE 5 is a view similar to FIGURE 4 showing a modified form of theblank.

FIGURE 6 is a schematic longitudinal cross-sectional view of the blankmembers of FIGURES 3 and 4 at one station in the series of assemblyoperations apart from the machine as a whole.

FIGURE 7 is a schematic longitudinal cross-sectional view of the sameblank member in a subsequent step in the method of assembly designatedas the initial heating station and showing in section a fragmentaryportion of the unit used to direct controlled hot air to the blankmembers.

FIGURE 8 is a longitudinal cross-sectional view of the same blankmembers in a subsequent step of the method showing diagrammatically themember used to curl the end marginal portion of the wall blank about theflange of the bottom blank.

FIGURE 9 is a schematic view of the same blank parts in a subsequentstep of the process illustrating the condition at the second heatingstage.

FIGURE 10. is a longitudinal sectional view showing the relation of theparts at a subsequent step generally referred to in the art as bottomexpansion.

FIGURE 11 is a side elevational view of one ofthe hot air units partlybroken away.

FIGURE 12 is an end elevational view of the unit of FIGURE 11.

FIGURE 13 is a sectional view along the line 13--13 of FIGURE 11.

FIGURE 14 is a cross-sectional view along the line 1414 of FIGURE 11.

FIGURE 15 is a longitudinal sectional view on an enlarged scale of afragmentary portion of a cup made in accordance with this invention bythe use of plasticcoated blank members.

FIGURE 16 is a view similar to FIGURE 15 by the use of blank membersplastic-coated on one side and metal foil laminated on the opposite sideof the side wall part.

Referring with more particularity to the drawing, the rotary turretshown in FIGURE 1 comprises a conventional hub member 21 havingfrustoconical mandrels 22 secured thereto and extending radiallyoutwardly therefrom. The turret is conventionally rotated intermittentlyby means (not shown), whereby the mandrels are successively positionedadjacent stations at which various steps in the process of forming thecups are carried out.

The sequence comprises, generally, placing on each mandrel at station Aa blank 23 that is to form the bottom section of the cup and then atsubsequent station C a blank 24 that is to form the side wall. The blank23 is disposed at the outer end of the mandrel and the blank 24 isdisposed around the circumference of the mandrel. The ends 25 and 26 ofthe blank 24 are lapped and secured together on the mandrel at station Cby conventional means not shown. At subsequent stations, these blanksare secured together to form the cup which is finally discharged fromthe mandrel.

In the process of forming cups from ordinary paper stock, the blank 23forming the bottom of the cup is secured to the side wall by gluing.When plastic-coated blanks are used, it is possible to dispense with theglue by heating the parts of the blanks to be joined together to thepoint of tackiness of the plastic coating. One method of accomplishingthis is described in US. Reissue Patent 25,302, wherein the blanks areheated to render the plastic tacky and then are moved relative to eachother to position the members in proper relation to each other.

A problem is involved in heating the plastic to the point of tackiness.A substantial amount of heat is required and the intervals of rest ordwell times of the mandrels at each station are quite short. Short dwellperiods on the order of 0.3 to 0.5 second are necessary in order toachieve an economical production capacity.

When the blanks are in their final position, heat is difficult topenetrate the layer of paper, paper being a substantial heat insulator.Consequently, in prior methods, the heat is applied directly to theplastic layer or to both sides of the paper stock where the plastic isto be heated to a point of tackiness in order to achieve the conditionof tackiness in the short interval of time available. In accordance withthe present invention, controlled heat is applied at two separatestations. At the first or preheating station D, the heat is applied inan amount just sutficient to bring the plastic coating to a condition ofimpending tackiness. For polyethylene coatings, a temperature of about750 F. is preferred when a dwell period of about 0.3 to 0.5 second isused. The heat is applied through the medium of hot air. At the secondheating station F, the temperature is increased and an added quantity ofheat is supplied to bring the coating to a condition of tackiness. Forpolyethylene plastic, a temperature of about 850 F. for the same dwellperiod has been found satisfactory for this purpose.

Between the station D and the station F, the blank parts 23 and 24 aresubjected to a conventional operation known as curling, whereby anannular marginal portion 25 of the blank 24 is bent around the flange 26of the blank 23 in preparation of a final forming step known as bottomexpansion. Consequently, as the heating station F is reached, the blankparts are in position for the final forming operation and the heating isprovided to effect or to cause the plastic to become tacky. The finalforming step takes place at station G and consists of the conventionalbottom expansion (see FIGURE whereby the curled portion 25 is pressedinto final position. This is diagrammatically illustrated in FIGURE 10by means of an inside roller 27 and an exterior anvil 28. However, inactual commercial operations, a more elabo rate mechanism is used. SeeUS. Patent No. 2,842,033.

At the succeeding station H, the completed cup is discharged from themandrel by directing a blast of air through an axial passageway 31 ofthe mandrel to a difiuser 32 having openings 33 at the periphery. Inpassing from the station H to station A, the mandrel is subjected to acooling operation by continuing the blast of air to bring itstemperature to a point below the softening tem erature of the plastic.Unless this were done, the blanks placed on the mandrel at the start ofthe cycle of operation would have their plastic coating become tacky.Hence, it would be difiicult, if not impossible, to manipulate the blankmembers on the mandrel. Also, the tacky plastic would foul the mandreland require wasteful stopping of the operation to clean them. Theefficiency of the operation from the standpoint of heat flow can besharply controlled by adjusting the amount of heat extracted at thispoint so as to prevent the plastic from becoming tacky and subsequentlyadding only that amount of heat required to supplement the residual heatin the mandrels at the station D.

The use of the preheating station D is especially important in themanufacture of cups from laminated materials, such as paper stock,having a laminated metal foil 34 on one side of the paper stock 35 andthe plastic coating 36 on the opposite side (see FIG. 5). Adhesivematerials 37 used to secure the laminates together soften under thetemperatures used to soften the plastic coating and may, in fact, be thesame material. Consequently, it is important that heat applied to thelaminated sheets be such as to avoid separation of these laminates. Thisis effectively accomplished in accordance with the present inventionwhere the final heating step to soften the coating is not applied untilthe blanks are in their final relative positions except for the bottomexpansion step. The latter step, however, does not adversely affect thelaminate bonding but, in fact, increases it under the pressure applied.Hence, the tendency of the laminates to separate is eifectively negatedand overcome.

The preheating station D and the final heating station F are eachequipped with a heater 38. These heaters at both stations are ofsubstantially the same construction but operated at differenttemperatures. Each comprises a cylindrical shell 39 of stainless steelor other oxidation resisting material, adapted to be disposed at thestations in alignment with the mandrels 22 as they come to rest at thesestations. The adjacent end of the cylinder is provided with a plate 40having a circular groove 41. The groove is provided with two radiallyspaced circular rows of apertures 42 and 43 on either side of the center44 of the groove. The center of the groove has substantially the samediameter as the bottom edge 45 of the cup so that the apertures 43 onthe inner row are directed toward the inside of the cup while the outerrow 42 is directed toward the outside. The plate 40 is secured to aninner flange 46 of retaining rings 47 of an outer cylinder 48 by meansof bolts 49.

On the interior of the cylindrical shell 39, there is mounted acylindrical core 50 of a diameter less than the inside diameter of theshell 39 so that it is disposed coaxially therewith in spaced relationto the shell. The core is held in the axial position by means of setscrews 51 passing through the shell and contacting the core.

The core is provided with a series of radial slots 52 that extendlongitudinally from one end of the core to the other end through whichair to be heated is directed from an outside source (not shown) into theshell through an opening 53 of an end wall 54 at the opposite end of theshell. The core is also provided with a pair of longitudinal bores 55and 56 in which there are embedded electrical heating elements 57 and58, respectively. A third longitudinal bore 59 is provided with athermocouple 60 for connection to a temperature gauge and regulator (notshown).

The shell 48 is provided with mounting lugs 61 and a sheet of insulation62 about the outer surface to reduce heat radiation losses.

Having described our invention, we claim.

1. A method of joining a closure disc having a peripheral flange to theend wall of a frustoconical shaped body to form an open-ended papercontainer comprising supporting said disc within the said body with theperipheral flange extending toward the end wall and the inside surfaceof the body and the surface of the flange adjacent said inside surfacehaving a thermoplastic coating therein, blowing hot air at one stationinto the hollow end against the parts to be joined until the coating ispreheated to a physical state of impending tackiness, causing the flangeof the disc and the end Wall to contact, rolling the edge of the endwall over the flange of the disc, said disc being in a position adjacentsaid end wall while the coating remains in a physical state of impendingtackiness, then blowing air at a higher temperature at a subsequentstation against the said parts until the coating becomes tacky andadhesive, then pressing the parts together, then cooling the parts torestore the polyethylene to its initial physical condition.

2. The method as defined by claim 1 in which the thermoplastic coatingis a polyethylene resin.

References Cited UNITED STATES PATENTS Bergstein 156227 Brown 9336.1Wills 156497 Von Hofe.

Olson et al.

Cummings 93-36.1 Harrison et al.

Monroe et al 156-497 X EARL M. BERGERT, Primary Examiner.

C. B. COSBY, Assistant Examiner.

US. Cl. X.R.

1. A METHOD OF JOINING A CLOSURE DISC HAVING A PERIPHERAL FLANGE TO THEEND WALL OF A FRUSTOCONICAL SHAPED BODY TO FORM AN OPEN-ENDED PAPERCONTAINER COMPRISING SUPPORTING SAID DISC WITHIN THE SAID BODY WITH THEPERIPHERAL FLANGE EXTENDING TOWARD THE END WALL AND THE INSIDE SURFACEOF THE BODY AND THE SURFACE OF THE FLANGE ADJACENT SAID INSIDE SURFACEHAVING A THERMOPLASTIC COATING THEREIN, BLOWING HOT AIR AT ONE STATIONINTO THE HOLLOW END AGAINST THE PARTS TO BE JOINED UNTIL THE COATING ISPREHEATED TO A PHYSICAL STATE OF IMPENDING TACKINESS, CAUSING THE FLANGEOF THE DISC AND THE END WALL TO CONTACT, ROLLING THE EDGE OF THE ENDWALL OVER THE FLANGE OF THE DISC, SAID DISC BEING IN A POSITION ADJACENTSAID END WALL WHILE THE COATING REMAINS IN A PHYSICAL STATE OF IMPENDINGTACKINESS, THEN BLOWING AIR AT A HIGHER TEMPERATURE AT A SUBSEQUENTSTATION AGAINST THE SAID PARTS UNTIL THE COATING